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Horizon-AGN virtual observatory - 2: Template-free estimates of galaxy properties from colours

Davidzon, I. and Laigle, C. and Capak, P. L. and Ilbert, O. and Masters, D. C. and Hemmati, S. and Apostolakos, N. and Coupon, J. and de la Torre, S. and Devriendt, J. and Dubois, Y. and Kashino, D. and Paltani, S. and Pichon, C. (2019) Horizon-AGN virtual observatory - 2: Template-free estimates of galaxy properties from colours. Monthly Notices of the Royal Astronomical Society, 489 (4). pp. 4817-4835. ISSN 0035-8711. doi:10.1093/mnras/stz2486.

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Using the HORIZON-AGN hydrodynamical simulation and self-organizing maps (SOMs), we show how to compress the complex, high-dimensional data structure of a simulation into a 2D grid, which greatly facilitates the analysis of how galaxy observables are connected to intrinsic properties. We first verify the tight correlation between the observed 0.3–5 μm broad-band colours of HORIZON-AGN galaxies and their high-resolution spectra. The correlation is found to extend to physical properties such as redshift, stellar mass, and star formation rate (SFR). This direct mapping from colour to physical parameter space still works after including photometric uncertainties that mimic the COSMOS survey. We then label the SOM grid with a simulated calibration sample to estimate redshift and SFR for COSMOS-like galaxies up to z ∼ 3. In comparison to state-of-the-art techniques based on synthetic templates, our method is comparable in performance but less biased at estimating redshifts, and significantly better at predicting SFRs. In particular, our ‘data-driven’ approach, in contrast to model libraries, intrinsically allows for the complexity of galaxy formation and can handle sample biases. We advocate that observations to calibrate this method should be one of the goals of next-generation galaxy surveys.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Davidzon, I.0000-0002-2951-7519
Capak, P. L.0000-0003-3578-6843
Ilbert, O.0000-0002-7303-4397
Masters, D. C.0000-0001-5382-6138
Hemmati, S.0000-0003-2226-5395
de la Torre, S.0000-0002-0839-2884
Devriendt, J.0000-0002-8140-0422
Kashino, D.0000-0001-9044-1747
Additional Information:© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2019 September 2. Received 2019 August 20; in original form 2019 May 30. Published: 05 September 2019. ID thanks Stefano Andreon, Sirio Belli, Micol Bolzonella, Keerthana Jegatheesan, Chris Hayward, and Lucia Pozzetti for useful discussions, and Elvira Tibi for all the rest. CL is supported by a Beecroft Fellowship. OI acknowledges the funding of the French Agence Nationale de la Recherche for the project ‘SAGACE’. This research was supported in part by the National Science Foundation under Grant No. NSF PHY-1748958 and by the NASA ROSES grant 12-EUCLID12-0004. The analysis presented in this work relied on the HPC resources of CINES (Jade) under the allocations 2013047012 and c2014047012 made by GENCI and on the Horizon and CANDIDE clusters hosted by Institut d’Astrophysique de Paris. We warmly thank S. Rouberol for maintaining these clusters on which the simulation was post-processed. This research is part of ERC grant 670193 and HORIZON-UK and is also partly supported by the Centre National d’Etudes Spatiales (CNES). Several python packages were used, including ASTROPY (Astropy Collaboration 2013; Price-Whelan et al. 2018) and SOMPY (main contributors: Vahid Moosavi, Sebastian Packmann, and Iván Vállas).
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Beecroft FellowshipUNSPECIFIED
Agence Nationale de la Recherche (ANR)SAGACE
European Research Council (ERC)670193
Centre National d'Études Spatiales (CNES)UNSPECIFIED
Subject Keywords:methods: data analysis –methods: statistical – galaxies: evolution – galaxies: fundamental parameters
Issue or Number:4
Record Number:CaltechAUTHORS:20190813-094655165
Persistent URL:
Official Citation:I Davidzon, C Laigle, P L Capak, O Ilbert, D C Masters, S Hemmati, N Apostolakos, J Coupon, S de la Torre, J Devriendt, Y Dubois, D Kashino, S Paltani, C Pichon, HORIZON-AGN virtual observatory – 2. Template-free estimates of galaxy properties from colours, Monthly Notices of the Royal Astronomical Society, Volume 489, Issue 4, November 2019, Pages 4817–4835,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:97859
Deposited By: Tony Diaz
Deposited On:13 Aug 2019 18:35
Last Modified:16 Nov 2021 17:34

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